Gasification of carbonaceous materials



,ing one modification of the same.

Patented Nov. 18, 1952 UNITED STATES ATENT OFFICE GASIFICATION FCARBONACEOUS MATERIALS ration of Belaware Application June 29, 1951,Serial No. 234,412

7 Claims. 1

The present invention relates to conversions involving the gasificationof carbonaceous materials. It is more particularly concerned with animproved process for maintaining the temperature in the conversion zone,such as a generator. In accordance with the present invention thetemperature in the generator, as for example, a water gas generator, ismaintained by withdrawing a portion of the carbonaceous material fromthe generator and passing it through a transfer line while in contactwith air for a relatively short time period. By operating in thismanner, a maximum production of carbon dioxide is secured as compared tocarbon monoxide, resultin in the maximum production of heat, for theamount of carbonaceous material circulated.

It is well known in the art to treat carbonaceous materials such as coalwith steam for the production of water gas. In this endothermicreaction, carbon reacts with steam to produce hydrogen and carbonmonoxide. Problems encountered in a coal gasification reaction of thischaracter are the coking of crushed coal or surplus coal fines, thegenerating of water gas from the coke with steam, and the supplying ofheat for the water gas generation. It is with this last problem thatthis invention is particularly concerned.

In accordance with the invention the temperature in a gas-producingconversion zone such as a water gas generator is maintained bywithdrawing a portion of the carbonaceous material from the generator,burning a portion of that withdrawn under conditions to produce themaximum amount of carbon dioxide and recycling the heated remainder tothe generation zone. This is extremely desirable because in burning tocarbon dioxide nearly three times as much heat is generated than whenburning to carbon monoxide (94.0 vs. 26.4 kg.-cal./mol of carbon),thereby minimizing the amount of carbon and air required to generate agiven amount of useful heat. Since the equilibrium in the presence ofcarbon very much favors formation of carbon monoxide at the temperaturesat which the heat must be generated, this can be accomplished only byminimizing the opportunity for reaction between the gas and solid phasesso as to discourage the slower secondary reaction, C+CO2 2CO,

while permitting the much faster primary reaction, C+O2- CO2 to proceed.Y

The process of the invention ,may be readily understood by reference tothe drawing illustratcarbonaceous material, as for example, coal orcoke, is withdrawn from coal hopper I through line 2 and introduced intoa water gas generator 3 by means of line 4. Steam is introduced intoline 4 by means of line 5. The amount of coal or coke introduced intothe water gas generator is controlled by means of slide valve 6.

In generator 3 there is shown a body of carbonaceous material indicatedby the reference character C. This material is in the form of a densefiuidized'mass havin an upper level at L above which, separated by aninterface, is a dilute phase. G represents a foraminous member such as agrid and the gasiform material from lines 4 and I2 entering the bottomof 3 pass through said forarninous member, which functions to affordgood distribution of gasiform ma terial entering the dense fluidized bedof carbonaceous material C.

The water gas generator is maintained at a pressure in the range fromabout atmospheric to lbs/sq. in. ga. while the temperature is maintainedin the range from about 1500 F. to 2100 F. The temperature is maintainedin water gas generator 3 in a manner as hereinafter described. Reactionproducts are withdrawn overhead from generator 3 by means of line i andintroduced into separation zone 8 wherein carbonaceous or ash productsare separated and removed by means of line 9; The water gas reactionproducts are removed from the system by means of line it and handled inany desirable manner. It may be desirable to recycle ash productsseparated in zone 8 in which case these products are removed by means ofline H and recycled to the generation zone 3. Sufficient and additionalsteam may be introduced by means of line 12. Slide valves l3 and I4control the amount of ash passing through lines H and 9, respectively.

In accordance with-the invention, carbonaceous materials are Withdrawnfrom water gas generator zone 3 by means of line l5. The amount ofcarbonaceous materials withdrawn is controlled by means of slide valveit. Mr is introduced by means of line I! and the air and carbonaceousmaterials pass through a relativelyyshort line It in order that the timeof contact between the carbonaceous materials and the air is relativelyshort. The reaction products are introduced into cyclone separation zoneIS in which the hot flue as is e a d and remo ed by means of line 2E.The e cases may-be handled in any d able. manner, a ,fzorex mpl p ss dhrou h he exchangers. Unburned carbonaceous materials are separated inseparation zone I9, withdrawn by means of line 2|, steam added by meansof line 22 and the heated carbonaceous materials then passed back towater gas generator zone 3 by means of line 4.

The process of the present invention may be widely varied. The inventionmay be adapted to any process wherein it is desirable to secure themaximum amount of heat by the burning of carbonaceous materials such ascoal, coke, or the like. For example, heat may be supplied in accordancewith the invention to such reactions as high and low temperaturecarbonization of carbonaceous solids, coking of hydrocarbonaceousmaterials particularly heavy hydrocarbonaceous residues includingreduced crude, asphalt, pitch, or the like, and similar reactions. Ofcourse in the case of starting materials which are liquid at thegasification conditions, suitable carrier solids such as coke, sand,pumice, etc. will be present in the gasification zone at least to startup the process, as it is well known in the art of fluid coking of suchmaterials.

The invention, however, is particularly adapted to a water gas generatorreaction in which it is desirable to maintain the temperature in thegenerator zone in a fixed range. In accordance with the presentinvention, coal or coke and air are contacted for a relatively shorttime period resulting in the maximum production of carbon dioxide andthe minimum production of carbon monoxide. Thus, to maintain thetemperature in the generator zone, it is possible to circulate a smalleramount of the carbonaceous material than would otherwise be the case ifequilibrium would be reached between carbon dioxide and carbon monoxide.

The time of contact between the air and the carbonaceous material may bevaried considerably. However, it is essential that the time of contactbe less than five seconds, preferably less than one second. It isespecially desirable to contact the air and coke for less than .'7second at a temperature in the range from about 1600 F. to 2200 F.

The present invention may be more fully understood by the followingexample illustrating modifications of the same.

Example Various operations were conducted in which air and coke werecontacted for the time periods shown. The results of these operationsare as follows:

plus carbon monoxide was about 12. The numbers in the last line indicatethe percent CO2 in C0 plus CO2 which will result, for each of thetemperatures, when long times for reaction are permitted.

This application is a continuation-in-part of our copending applicationSerial No. 663,230, filed April 18, 1946, now abandoned.

The process of the present invention is not to be limited by any theoryas to mode of operation but only in and by the following claims in whichit is desired to claim all novelty insofar as the prior art permits.

What is claimed is:

l. A process for forming a gaseous fuel from finely divided solidcarbonaceous material, which comprises charging fresh powdered solidcarbonaceous material to a gaseous fuel generation zone, charging steamto said generation zone where it contacts said charged carbonaceousmaterial at temperatures within the range of from about 1500 F. to 2100F., causing the steam to flow upwardly in said generation zone at asufficiently low rate so as to cause the said carbonaceous materialundergoing treatment to form a fluidized bed, withdrawing carbonaceousmaterial from said generation zone, mixing the withdrawn carbonaceousmaterial with an oxygen containing gas and causing the said carbonaceousmaterial to undergo at least partial combustion to add heat to saidcarbonaceous material, while the said carbonaceous material is in theform of a confined stream in a zone of restricted crosssection, limitingthe time period of combustion of said carbonaceous material within thelimits of from about 0.5-0.7 second, separating the unburnt carbonaceousmaterial from the resulting combustion fumes to prevent substantialreduction of the formed carbon dioxide and returning the thus heatedcarbonaceous material to the said generation zone for the purpose ofsupplying the heat necessary to support the gaseous fuel generationtherein taking place.

2. The method of claim 1 in which the carbonaceous material withdrawnfrom the reaction zone is subjected to the influence of air for asufficiently short period of time such that of the oxides of carboncontained in the combustion fumes, up to 36% is in the form of carbondioxide.

3. A process for producing gasiform fuels from carbonaceous materials,which comprises charging fresh carbonaceous material to a gasificationzone containing a dense turbulent bed of car- Oper 1 Oper. 2 Oper. 3Opel-.4 Oper 5 Time of contact (see) .66 .56 .56 53 10 Temperature, F l,725 l, 900 1, 700 l, 900 1,800 Flue Gas Analysismol percent:

02 18.3 14.4 18.2 16.3 3.6 3. 1 9. 7 3. 8 6. 4 27. 0 0. O 0. 1 0. 0 0. 20. 0 78. 6 75. 8 78. 0 77. 1 69. 4 n CO-i-C 86 60 83 72 12 Percent C 0;in C 0+0 0: at equilibrium [or Cori-S200 1.5 0.25 2.8 0.25 0

From the above, it is readily apparent that by operating in accordancewith the present invention, in this case, at times less than about onesecond, substantial improvements will be secured. For example, thepercentage of CO2 in the total carbon dioxide plus carbon monoxidevaried from to 86% when the time was 0.5-0.7 second whereas when arelatively long time of contact (10 seconds) was employed, thepercentage of carbon dioxide as compared to carbon dioxide 75 form of aconfined stream in a zone of restricted cross-section, limiting theresidence time of said last-mentioned gas in contact with saidcarbonaceous solids to a period of less than about 0.7 second at atemperature higher than said gasification temperature, separating theunburned carbonaceous solids from the resulting combustion fumes toprevent substantial reduction of the formed carbon dioxide and returningthe thus heated carbonaceous solids to the said zone for the purpose ofsupplying the heat necessary to support the gasification taking placetherein.

4. The process of claim 3 in which said higher temperature is 1600F.-2200 F.

5. A process for supplying heat to the conversion of carbonaceousmaterials, which comprises charging fresh carbonaceous material to aconversion zone containing a dense turbulent bed of carbonaceous solidsmaintained at a con version temperature and fluidized by upwardlyflowing gases to resemble a boiling liquid, withdrawing carbonaceoussolids from said zone, mixing the withdrawn carbonaceous solids with afree oxygen-containing gas and causing the said carbonaceous solids toundergo at least partial combustion to add heat to said carbonaceoussolids, while the said carbonaceous solids are in the form of a confinedstream in a zone of restricted cross-section, limiting the residencetime of said last-mentioned gas in contact with said carbonaceous solidsto a period of less than 1 second at a temperature higher than saidconversion temperature, separating the unburned carbonaceous solids fromthe resulting combustion fumes to prevent substantial reduction of theformed carbon dioxide and returning the thus heated carbonaceous solidsto the said zone for the purpose of supplying the heat necessary tosupport the conversion taking place therein.

6. The process of claim 5 in which said period is less than 0.7 second.

7. The process of claim 6 in which said higher temperature is 1600F.-2200 F.

HERBERT G. M. FISCHER. ALBERT B. WELTY, J R.

No references cited.

1. A PROCESS FOR FORMING A GASEOUS FUEL FROM FINELY DIVIDED SOLIDCARBONACEOUS MATERIAL, WHICH COMPRISES CHARGING FRESH POWDERED SOLIDCARBONACEOUS MATERIAL TO A GASEOUS FUEL GENERATION ZONE, CHARGING STEAMTO SAID GENERATION ZONE WHERE IT CONTACTS SAID CHARGED CARBONACEOUSMATERIAL AT TEMPERATURES WITHIN THE RANGE OF FROM ABOUT 1500* F. TO2100* F., CAUSING THE STEAM TO FLOW UPWARDLY IN SAID GENERATION ZONE ATA SUFFICIENTLY LOW RATE SO AS TO CAUSE THE SAID CARBONACEOUS MATERIALUNDERGOING TREATMENT TO FORM A FLUIDIZED BED, WITHDRAWING CARBONACEOUSMATERIAL FROM SAID GENERATION ZONE, MIXING THE WITHDRAWN CARBONACEOUSMATERIAL WITH AN OXYGEN CONTAINING GAS AND CAUSING THE SAID CARBONACEOUSMATERIAL TO UNDERGO AT LEAST PARTIAL COMBUSTION TO ADD HEAT TO SAIDCARBONACEOUS MATERIAL, WHILE THE SAID CARBONACEOUS MATERIAL IS IN THEFORM OF A CONFINED STREAM IN A ZONE OF RESTRICTED CROSSSECTION, LIMITINGTHE TIME PERIOD OF COMBUSTION OF SAID CARBONACEOUS MATERIAL WITHIN THELIMITS OF FROM ABOUT 0.5-0.7 SECOND, SEPARATING THE UNBURNT CARBONACEOUSMATERIAL FROM THE RESULTING COMBUSTION FUMES TO PREVENT SUBSTANTIALREDUCTION OF THE FORMED CARBON DIOXIDE ADN RETURNING THE THUS HEATEDCARBONACEOUS MATERIAL TO THE SAID GENERATION ZONE FOR THE PURPOSE OFSUPPLYING THE HEAT NECESSARY TO SUPPORT THE GASEOUS FUEL GENERATIONTHEREIN TAKING PLACE.